Solar cells are roughly classified based on the materials into three groups: silicon, compound, and organic solar cells. Silicon solar cells have high conversion efficiency, and solar cells using polysilicon are most widely used for power generation. A dye-sensitized solar cell (hereinafter, may be abbreviated as “DSC”) is known as one of the organic solar cells. Although the conversion efficiency of DSCs is inferior to that of silicon solar cells, DSCs have an advantage that the manufacturing cost is lower than those in the cases of using inorganic semiconductors, as in silicon and compound solar cells, and have attracted attention in recent years. In addition, DSCs have an advantage that high power generation efficiency can be obtained even in a low-illuminance environment and have attracted attention also from this point of view.
However, dye-sensitized solar cells have a problem in durability. Accordingly, it has been investigated to improve the durability of sensitizing dyes (hereinafter, simply referred to as “dyes”) (for example, PTL 1).